Lecture 20 BIO 311D 2nd EditionOutline of Last Lecture I. Recap hormone experimentsII. Mutualism with N-fixing bacteriaIII. Plant defenses Outline of Current Lecture I. Plant DefensesII. Evolution of plant reproductionCurrent LectureI. Plant DefensesA) Discuss two strategies (one structural adaptation and one biochemical adaptation) used by plants to deter herbivores. Describe plant strategies to defend against pathogensCactus: thorns, discourages herbivores from eating from it and reduces loss of waterTrichomesB) Plant Enemies and DefensesPlant defensive responses can be constitutive (always present) or induced (produced in response to damage or stress) Nicotine, Alkaloids, Tannins, Pyrethrin, Digitalis, Latex C) Plants such as milkweeds produce sticky latex and other substances to deter herbivores, but… Monarch caterpillarsD) Response to herbivore damage: pathway to gene activation and production of defensive compounds – Plant secondary compounds are toxic to insects 1. Wounding / Chemical in saliva (caterpillar lands on the plant)2. Signal transduction pathway (caterpillar) 3. Synthesis and release of volatile attractants (caterpillar) 4. Recruitment of parasitoid wasps that lay their eggs within caterpillars (moth)E) Plant cells can have receptors that directly detect molecules from pathogens and trigger signal transduction. In response, cells turn on genes for production of antimicrobial proteins and also release “alarm signals”F) Hypersensitive response: damaged tissue sends signal so other tissues acquire resistance (remain free of microbe); the pathogen is contained and prevented from spreading when cells around it seal it off, then die. - Infected cells produce anti-microbial compounds- Infected cells close off plasmodesmata and thicken cell walls- Plant warning signals released into phloem, included salicylic acid G) Develop a scenario (i.e. list a series of steps of adaptation by natural selection) in which there is an “evolutionary arms race” between a plant and either 1. An herbivore or2. A pathogenic microbe Plant would develop a poison that could harm the herbivore (caterpillar, beetle, etc.) Plant evolves as the herbivores develop counter-strategies Why don’t all plants produce distasteful or noxious compounds in their leaves to discourage animal herbivores?H) Phytochemicals- compounds produced by plants but not considered essential nutrients:- Antioxidants- Defenses against bacteria, viruses, fungi- Defenses against herbivorous animals - People are taking advantage of these plant defensive compounds, using many as nutritional supplements to fight human disease II. Evolution of Plant ReproductionA) Plant reproduction relies on intra-species, inter-species, and intercellular communication B) Asexual reproduction (vegetative): by budding or fragmentation, by runners or root spreading- Quaking Aspen trees- many individuals in a clone, connected by their roots C) Sexual life cycles always involve meiosis and fertilization. What is the pattern for plant life cycles?D) Angiosperms: a flower is the sexual reproduction of Angiosperms - Monocots: flower parts in 3’s- Dicots: flower parts in 4’s and 5’s (or multiples)+ Flower Parts are part of the diploid sporophyte generation- Petals: for attracting pollinators- Sepals: for protection or attraction- Carpel (with ovary): egg production- Anthers (on stamen): pollen production E) A gametophyte is a multicellular haploid plant. In vascular plants, the gametophyte is tiny.- In flowering plants: + Male gametophyte is the pollen grain (a few haploid cells)Pollen grain is NOT the sperm nucleus. The pollen grain doesn’t fertilize. It is part of pollination. + Female gametophyte is the embryo sac (contains 8 haploid nuclei, a few cells) F) Big picture of alternation of generations in flowering plants. What is the diploid sporophyte? What is the haploid gametophyte? - The alternation of generations life cycle in a flowering plant?Sporophyte (diploid) meiosis gametophyte gametes fertilization diploid
View Full Document
Unlocking...